The invention discloses a steam generator capable of avoiding emission of radioactive materials. The steam generator is connected between a primary loop and a secondary loop of nuclear power equipment, and comprises a housing and a separated heat pipe loop circuit; the housing comprises a left chamber and a right chamber which are sealed and separated from each other; the left chamber is in circulating communication with the primary loop; the right chamber is in circulating communication with the secondary loop; the separated heat pipe loop circuit comprises an evaporation segment and a condensation segment; the evaporation segment is placed in the left chamber and immersed in the coolant liquid of the primary loop; the condensation segment is placed in the right chamber and immersed in the coolant liquid of the secondary loop; the outlet and the inlet of the evaporation segment are respectively communicated with the inlet and the outlet of the condensation segment; the horizontal position of the evaporation segment is lower than that of the condensation segment. Through the adoption of the steam generator, the phenomenon that contaminated water in the primary loop directly enters the secondary loop to further leak to the outside environment, which is caused by the break of a heat transferring pipe of a traditional steam generator, is avoided, so that the reliability and the safety of a nuclear power plant are improved.